Hardness classification of stainless steel pipes

Stainless steel pipes are generally measured by three hardness indicators: Brinell, Rockwell and Vickers.
Brinell hardness
Among the stainless steel pipe standards, Brinell hardness is the most widely used, and the hardness of the material is often expressed by the indentation diameter, which is both intuitive and convenient. However, it is not suitable for steel pipes of harder or thinner steel.
Rockwell hardness
The Rockwell hardness test of stainless steel pipe is the same as the Brinell hardness test, which is an indentation test method. The difference is that it measures the depth of the indentation. Rockwell hardness test is a widely used method, among which HRC is second only to Brinell hardness HB in steel pipe standards. Rockwell hardness can be used to measure metal materials from extremely soft to extremely hard. It makes up for the inadequacy of the Brinell method. It is simpler than the Brinell method, and the hardness value can be read directly from the dial of the hardness machine. However, due to its small indentation, the hardness value is not as accurate as the Brinell method.
Vickers hardness
Vickers hardness test of stainless steel pipe is also an indentation test method, which can be used to determine the hardness of very thin metal materials and surface layers. It has the main advantages of Brinell and Rockwell methods, and overcomes their basic shortcomings, but it is not as simple as the Rockwell method, and the Vickers method is rarely used in steel pipe standards.
Hardness testing
For annealed stainless steel pipes with an inner diameter of more than 6.0mm and a wall thickness of less than 13mm, the W-B75 Webster hardness tester can be used. For stainless steel pipes with an inner diameter greater than 30mm and a wall thickness greater than 1.2mm, use a Rockwell hardness tester to test HRB and HRC hardness. The inner diameter of the stainless steel tube is greater than 30mm and the wall thickness is less than 1.2mm. The surface Rockwell hardness tester is used to test the HRT or HRN hardness. For stainless steel pipes with an inner diameter of less than 0mm and greater than 4.8mm, use a Rockwell hardness tester for pipes to test HR15T hardness. When the inner diameter of the stainless steel pipe is greater than 26mm, the hardness of the inner wall of the pipe can also be tested with a Rockwell or surface Rockwell hardness tester.